Device for adjusting the tension of yarn fed to a yarn comsuming machine

ABSTRACT

A device for feeding a high-stretch yarn to a yarn-consuming machine at a constant speed and tension in which a delivery yarn guide supplies the yarn at an uncontrolled tension to a pair of rollers driven at different speeds over which the yarn is looped, which rollers impart to the yarn a constant speed and a tension which is higher than the decrimping tension and subsequently ease the imparted tension so that the yarn assumes a hysteresis characteristic relative to the stretch/load curve of the yarn produced by the application of the imparted tension so as to achieve a delivery tension but which may be varied without the production of appreciable variation in length of the yarn.

United States Patent [72] lnventors Bernard-Francois Helfl'er Divisionof Ser. No. 550,715, May 17, 1966,

Pat. No. 3,451,603

Mar. 2 l 97 1 Institut Textile De France Boulogne S, Seine, France 45]Patented [73] Assignee [54] DEVICE FOR ADJUSTING THE TENSION 0F YARN FEDTO A YARN COMSUMING MACHINE 5 Claims, 5 Drawing Figs.

[52] US. Cl 242/47.08 [51] Int. Cl B65h51/08 [50] Field of Search242/47.08,

Primary Examiner-Nathan L. Mintz Attorney-Mason, Fenwick and LawrenceABSTRACT: A device for feeding a high-stretch yarn to a yarn-consumingmachine at a constant speed and tension in which a delivery yarn guidesupplies the yarn at an uncontrolled tension to a pair of rollers drivenat different speeds over which the yarn is looped, which rollers impartto the yarn a constant speed and a tension which is higher than thedecrimping tension and subsequently ease the imparted tension so thatthe yarn assumes a hysteresis characteristic relative to thestretch/load curve of the yarn produced by the application of theimparted tension so as to achieve a delivery tension but which may bevaried without the production ofappreciable variation in length of theyarn.

PATENTEU MAR 2197! SHEET 1 BF 3 will I HIHII Hllllllllllllllllllllllllmllllllllll BERNARD-FRANCOIS HELFF'EE,

A T TOE/VEVS DEVICE FOR ADJUSTING THE TENSION F YARN FED TO A YARNCOMSUMING MACHINE This application is a division of application Ser. No.550,7l5 of the same inventors filed May 17, 1966 now U.S. Pat. No.3,451,603.

The present invention relates to a thread feed device intended to beused primarily for feeding hosiery knitting or other yarn consumingmachines.

On a knitting machine, the yarn, while passing through a certain numberof straddling devices such as yarn guides, yarn breakers, throwers andthe like, is fed from the bobbin to the needles without being controlledat any point in its path, by a device for checking its unwinding speed.Experience shows that the unwinding of the yarn is not uniform, eitheras between-one yarn and another, or as between one portion and anotherof the same yarn. This is mainly due to the frictional forces to whichthe yarn is subjected at various points before it reaches the needles.While the yarn is leaving the spool, moreover, the latter is frequentlyjerked, which also contributes to the creation of undesirableirregularities.

To remedy these difficulties, it has already been proposed that thereshould be interposed, between the bobbin and the needles of a knittingmachine, a yarn feed device with which either the tension or the speedof the thread might be regulated. One such yarn feed device with whichthe speed of the yarn can be kept constant, consists of a frustoconicaldrum, mounted to rotate about its longitudinal axis, and a yarn guidefixed rigidly to a lever, to the other end of which is fitted arestoring spring that causes the lever to swing, to a certain extent, sothat the yarn passing through the guide is wound once or several timesaround the frustoconical drum and rises towards the top or falls towardsthe base of the drum, in order to keep the thread under constanttension. Obviously, with the drum rotating at a particular speed, thespeed of the yarn as it leaves the drum varies with the changes in thedrum diameter where the the yarn is wound onto it.

Another previously suggested yarn feed, which consists likewise of afrustoconical drum and a yarn guide movable on an axis parallel to oneposition of the line generating the inclined face of the frustoconicaldrum, enables the speed at which the yarn leaves the drum to be keptconstant. In this device, the yarn is wound once around the drum, to theface of which it adheres strongly, this face generally being made of amaterial possessing a high coefficient .of friction, such as rubber. Forany given diameter at which the yarn is wound about the drum, the yarnwill leave the drum at a constant speed, that is to say, giving aconstant feed but, with this device, one cannot closely control thethread tension in the case of a textured yarn.

With another previously suggested yarn feed device it is possible toeliminate the variations in yarn tension due to variations in the speedof unwind from the bobbin. This feed device comprises a drum to whichrotary motion is imparted and which consists of two truncated conesfollowing each other along the axis of the drum and joined bya'frustoconical bevel, associated yarn guides being so placed inrelation to the drum that the yarn, during the first part of its pathfrom bobbin to needle, makes contact with the first truncated cone alongan arc of a circle and then, during the second part of its path, firstlywith the same truncated cone along a helical path diametrically oppositethe circular arc and then with the frustoconical bevel, the yarn finallymaking contact, during a third part of its path, with the secondtruncated cone along a circular are equal to that defined on the firsttruncated cone by the first part of the path of the yarn. By reason ofthe particular path followed, the yarn is subjected to a given tensionduring the first part of this path, to a higher tension during thesecond part of its path and, finally, in the third part of its path to atension equal to the first. In general terms, this yarn feed preventsthethread from slipping on the drum.

These previously proposed yarn feed devices, and the methods that can beused with their aid, are more or less well suited to feeding hosieryknitting machines with nontextured, that is to say, low-stretch,threads. However, when yarns likely to stretch considerably, such astextured threads (crimped yarns) are to be used, the previously proposedfeed devices and the feeding methods made possible by their use do notenable the yarn tension and speed to be kept constant, because suddenchanges in tension beyond the feed device may cause the yarn to slipthereon.

High-stretch yarns, such as crimped yarns, elastometers and the like,are known to be characterized by very high variations in stretch forvery small changes in loading force. If we look at the load/stretchcurve for such a thread, we find that, in an initial zone which we maycall the uncurling, uncrimping, or curl elongation zone, the variationsin stretch for small changes in the load are very large. Beyond thiszone the variations with load in the stretch of the yarn is very small,even for considerable changes in tension or loading. The length (inother. words, the speed) of a high-stretch yarn could therefore becontrolled if the tension applied to it lay beyond the uncurling zone.This means that the tension should be higher than 0.1 gram/denier, or0.9 g./tex. Even for ZOO-denier thread, however, this would make atension equivalent to a load of 20 g.; and in the case of a texturedyarn used in a knitting machine, one cannot knit at such high tensionswithout running into trouble.

The object 'of the present invention is to provide a feed device wherebyyarn consuming machines, and knitting machines in particular, can be fedwith high-stretch yarn at substantially constant speed and undersubstantially constant tension. 7

The present invention is directed to a yarn feed device for feeding ahigh-stretch yarn to a yarn consuming machine at a constant speed andtension, said device comprising means for supplying the yarn at a highbut uncontrolled tension over a first part of its path, means forimparting to the yarn a constant speed and a high tension over a secondpart of its path, the said high tension being beyond the decrimpingtension of the load/stretch curve of the yarn, and means for easing inthe yarn said high tension over a third part of its path so as toachieve a relatively lower delivery tension, the value of which lowertension lies below the decrimping tension of the said curve. The termdecrimping tension when used herein means the tension required to removesubstantially all of the crimping from a given yarn.

The subject invention is also directed to a device in which the yarnfeed enables a knitting machine with which it is associated toexpeditiously change from continuous to noncontinuous knitting withcomplete control of tension. This result is effected by the employmentof a yarn feed device in which two conical drums are rotating atconstant revolutions per minute with different portions along thesurface of each drum having different peripheral speeds. A guide memberis provided at the delivery drum of the yarn feed device for positioningand holding the yarn against the periphery of the delivery drum withyarn in engagement with the other drum being engaged with a portion ofthe drum surface moving at a speed less than the speed of the portion ofthe delivery drum engaged by the yarn.

In other embodiments the yarn is fed over a delivery and an infeedcylinder with the delivery cylinder being driven faster than the infeedcylinder and with a pressure member being provided to urge the yarnagainst at least the delivery drum.

The manner in which the objects of this invention are accomplished bythe following described embodiments will be better understood withreference to the accompanying drawings in which:

FIG. 1 is a plan view showing a first embodiment of a thread feed devicein accordance with the invention;

FIG. 2 is an end elevation of the feed device of FIG. 1;

FIG. 3 is an end elevation of a second embodiment of the feed device;

FIG. 4 is an end elevation of a third embodiment feed device; and

FIG. 5 is a graph of the load/stretch curve illustrating hysteresis of atextured thread for example HELANCA-IOO-d (Registered Trademark).

In the graph of FIG. 5, the abscissae represent the loading in gramsapplied to a textured thread (crimped yarn) of given initial length 0.50m., the ordinates representing the stretch L in centimeterscorresponding to a given loading. High-stretch yarns such as crimpedyarn, elastometer filaments and the like are known to be characterizedby very high variations in stretch for small changes in loading. If theload/stretch curve R of such a yarn is considered, it will be observedfor a zone lying between the origin and the point H, which may be calledthe uncrimping or crimping elongation curve, that the variations in thestretch of the yarn are clearly larger than for equal changes in theloading to which it is subjected beyond this zone, that is to say, abovethe point H, where an increase in the yarn loading results in onlyslight further elongation. In fact, from curve R, it willbe seen that,for one end and the same load variation, AC, the stretch variation ALobtained in uncrimping zone OH is far larger than the stretch variationAL: obtained in that part of the curve which lies beyond point H. Thismeans that it is possible to control the length of yarn taken only whenthe tension applied to it is equal to or greater than the value H, whichis approximately 0.1 g./denier. It must be recognized, however, thatthis represents, for a ZOO-denier yarn, a load of 20 grams, and that onecannot knit at such high tension without encountering difficulties. Ifthe load on the yarn be first increased to a value K and then reduced,the resulting curve S lies above the curve R and shows a givenhysteresis, so that one can reduce the yarn tension to valuessubstantially lower than value H without thereby affecting the length ofyarn delivered, that is to say, without the yarn undergoing anyconsiderable reduction in length.

The yarn feed devices in accordance with the invention serve to applythe results of this experiment.

In one advantageous form, the device comprises two frustoconical drums Aand B (FIG. 1), of suitable dimensions for covering the entire range oftightness of the knitting or other yarn consuming machines. These twodrums may be identical to or differently shaped from each other. In onesuch pair of drums A and B (as illustrated), they are situated side byside with their axes parallel and are covered with a facing having ahigh coefficient of friction to prevent the yarn from slipping. Thisfacing may, for example, be made of rubber. On the base of each of thefrustoconical drums is mounted a pinion, the pinion spindles beingjournaled in suitable bearings (not shown). Gearwheel mounted betweenthe two drums meshes with each of the drum pinions. These two drums aremechanically driven from a motor (not shown) through the said gearwheeland may each rotate at the same speed and in the same direction. Itwould be equally possible to drive the drums in opposite directions andat different speeds. Each driving drum A and B is associated with atakeup yarn guide 1 and 3 respectively, and a delivery yarn guide 2 and4 respectively. Takeup yarn guides 1 and 3 and delivery yarn guides 2and 4 are rigidly attached to runners 5 and 6 respectively, mounted on aworm thread 7 and 8 respectively, along which they can move axially. Aseparate guide rod (not shown) passes through each runner 5 and 6 inorder to prevent its rotation about thread 7 or 8. Each worm thread liesnear the corresponding frustoconical drum and parallel to a linegenerating then sloping face thereof or to the axis thereof. By

rotating the thread 7 or 8, it is possible to obtain the desiredindependent positioning of each runner, with its takeup yarn guide anddelivery yarn guide, in relation to the frustum height of thecorresponding drum A or B. Yarn F arriving at an uncontrolled speed andtension from a supply bobbin (not shown), passes through the takeup yarnguide 1 of the first drum A, passes once completely around this drum andthrough the delivery thread guide 2 and is then led to the takeup yarnguide 3 of the second drum B. The yarn then passes once completelyaround the drum B and on through the delivery yarn guide 4, before beingtaken to the knockingdown cam and from there to the needles.

Each drum A and B enables yarn to be delivered at a given constant speedfor a given speed of rotation, which is the same for each drum, thespeed of delivery of the yarn from each drum being determined by thediameter of that section of the drum around which the yarn is wound.Three cases can arise: the yarn delivery speed of the drum A is lowerthan the yarn delivery speed of the drum B; or the delivery speed fromdrum A is equal to that from the drum B; or the delivery speed from thedrum A is higher than that from the drum B. It is only the first ofthese cases with which this embodiment is concerned. If the position ofthe yarn guides 3 and 4 at the drum B is so adjusted that the yarn isdelivered from the drum A at a lower speed than from the drum B,stretching of that part of the yarn which lies between the two drumswill take place, i.e. a first part of its path, so that the tension onthis part of the yarn will be increased. This yarn tension between thetwo drums will be termed the intermediate tension T Preferably, theintermediate tension is up to 10 times higher than the tension atdelivery.

The positioning of the runner 6', with its yarn guides 3 and 4, makes itpossible, after passing partly around the drum B which constitutes asecond part of its path, to obtain from the second drum the yarndelivery speed at a third part of its path requisite for the desiredlength of stitch. The positioning of the runner 5, with its yarn guides1 and 2, enables the speed of delivery of the yarn from the first drumA, to be so determined as to produce the correct intermediate tension Tbetween the drums A and B. The takeup tension T of the yarn F prior toits admission to the feed device at the yarn guide 1 may vary and may beof any value. The delivery tension T of the yarn F after its passagethrough the feed device and between this and the yarn consuming machine(that is to say, in the case of a knitting machine, the needles), isregulated to the desired value by suitable positioning of theknocking-down cam of the knitting machine (not shown).

Thus, with the aid of a feed device hereinbefore particularly described,it is possible to use a method of feeding high-stretch yarn to a hosieryknitting or other yarn consuming machine at constant speed and tension,the tension at which the yarn reaches the machine remaining low, thismethod comprising, the steps of subjecting the yarn to tension which ishigher than the decrimping tension, such as to bring it into aload/stretch zone in which variations in the loading applied to the yarndo not result in appreciable stretching, and then in reducing thetension in accordance with the hysteresis characteristic, whereby aconsiderable reduction in loading does not produce appreciable variationin the length of the yarn; so that the yarn delivery and the low tensionon the yarn reaching the yarn consuming machine (and, more particularly,the needles of a knitting machine) remain strictly constant,irrespective of the speed and tension at which the yarn is taken up bythe feed device. 4

Instead of frustoconical drum rotating at equal peripheral speeds andwinding the same yarn, of which the loop round the first drum is smallerin diameter than the loop round the second drum, it is possible toemploy cylindrical drums, the first rotating at a lower peripheral speedthan the second. The feed device can be used not only with a hosieryknitting machine, but can also be applied to any machine or mechanismwhich requires yarn at a strictly controlled speed and tension.

A yarn feed device shown in FIGS. 3 and 4 has two cylindrical drivingdrums 11 and 12 spaced apart from each other.

In general terms, the takeup drum 11 turns at a lower peripheral speedthan the delivery drum 12. The drums 11 and 12 may be driven by a singlemotor, a variable speed gearbox (not shown) being interposed between thetwo drums to provide any desired differences in peripheral speeds.

In the second embodiment shown in FIG. 3, the delivery drum 12 isprovided with a device 13 for holding other yarn with part of thesurface of the drum 12. This device 13 consists of two rollers 14 and15, spaced apart from each other and mounted on one end and the samesupport (not shown). This support is adjustable and enables the rollers14 and 15 to be brought towards or moved away from the drum 12. The tworollers 14 and carry an endless belt 16, which, like the drum 12, has ahigh coefficient of friction. The endless belt is driven either by oneof the rollers 14 and 15 or by the drum l2.

The yarn F, in this case, passes around the first drum 11,- without thefriction force necessarily being the same between the starting up andthe normal running of the feed device. After passing once completelyaround the first or braking drum 11, yarn F is applied against part ,ofthe face of the drum 12 by the endless belt of the device 13. Hence, theyarn F moves at the same speed at any point on the periphery of the drum12. Since the peripheral speed of the drum 12 is higher than that of thedrum 11, yarn F undergoes stretching while passing between these twodrums, accompanied by the intermediate tension hereinbefore referredto.

For the knitting of adjoining edges or-heel reinforcements, I

the device 13 is moved clear of the drum 12. By reason of its beingwound around the drum 11, the yarn F is still well controlled as regardstension.

In the third embodiment shown in FIG. 4, the takeup drum 11 in the yarnfeed device is likewise provided with a device' thus firmly held againstboth drumsll and 12 and is bound to move at speeds equal to theperipheral speeds of the two i drums. Because of the difference in speedbetween the first drum and the second, the yarn F is subjected totension between drums 11 and 12. To free the yarn F, all that isrequired is to move devices 13 and 13 away from drums 11 and 12. It isequally possible, of course, for these devices 13 and 13' to bestationary and for drums 11 and 1,2 to be adjustable in relation tothem.

We claim:

1. A yarn feed device for feeding a high-stretch yarn to a yarnconsuming machine at a contact speed and tension, said devicecomprising: means for supplying the yarn to the device at anuncontrolled tension; means for imparting to the yarn, over a first partof its path a constant speed and a tension which is higher than thedecrimping tension; and means for casing in the yarn the said impartedtension over a second part of its path so that the yarn assumes ahysteresis characteristic relative to the stretch/load curve of the yarnproduced by application of the high tension such that over a third partof its path a delivery tension is achieved which is lower than thedecrimping tension whilst permitting a variation of tension to betolerated without the production of appreciable variation in length ofthe yarn.

2. A yarn feed device according to claim 1 wherein the constant speedand tension imparting means comprises two rotatably mountedfrustoconical drums, the peripheral surface of each of which has a highcoefficient of friction, and yarn guide means arranged to lead yarninitially onto the surface of the first drum, thence onto the surface ofthe second drum and finally away from the latter, said yarn guide meansserving further so to direct the yarn that the speed of that part of theyarn which is in contact with the surface of the first drum is lowerthan the part of the yarn in contact with the second drum. 1

3. A yarn feed device according to claim it wherein the constant speedand tension imparting means comprises two rotatably mounted cylindricaldrums, the peripheral surface of holding device comprises two spacedrollers and an endless belt passes around both said rollers and 19arranged so as to be capable of being brought into contact with saidpart of the surface of the second drum.

1. A yarn feed device for feeding a high-stretch yarn to a yarnconsuming machine at a contact speed and tension, said devicecomprising: means for supplying the yarn to the device at anuncontrolled tension; means for imparting to the yarn, over a first partof its path a constant speed and a tension which is higher than thedecrimping tension; and means for easing in the yarn the said impartedtension over a second part of its path so that the yarn assumes ahysteresis characteristic relative to the stretch/load curve of the yarnproduced by application of the high tension such that over a third partof its path a delivery tension is achieved which is lower than thedecrimping tension whilst permitting a variation of tension to betolerated without the production of appreciable variation in length ofthe yarn.
 2. A yarn feed device according to claim 1 wherein theconstant speed and tension imparting means comprises two rotatablymounted frustoconical drums, the peripheral surface of each of which hasa high coefficient of friction, and yarn guide means arranged to leadyarn initially onto the surface of the first drum, thence onto thesurface of the second drum and finally away from the latter, said yarnguide means serving further so to direct the yarn that the speed of thatpart of the yarn which is in contact with the surface of the first drumis lower than the part of the yarn in contact with the second drum.
 3. Ayarn feed device according to claim 1 wherein the constant speed andtension imparting means comprises two rotatably mounted cylindricaldrums, the peripheral surface of each of which has a high frictioncoefficient and each of which is capable of being rotated at differentspeeds.
 4. A device according to claim 3, comprising an adjustabledevice arranged to hold the yarn in engagement with part of the surfaceof the second drum, thereby preventing slippage of the yarn.
 5. A deviceaccording to claim 4, wherein said adjustable holding device comprisestwo spaced rollers and an endless belt passes around both said rollersand is arranged so as to be capable of being brought into contact withsaid part of the surface of the second drum.